1. Field of the Invention
The present invention relates to a device for detecting thermal energy in the infrared spectrum. The device detects the level of the infrared thermal energy emitted from the exhaust port of an engine, and in particular an engine mounted on a helicopter.
2. Prior Art
Heat seeking missiles which home on the infrared thermal energy emitted from an engine are known, as are suppressors for suppressing the level of the thermal energy emitted to thereby break the homing connection, and consequently the threat to the aircraft. The suppressors may unexpectedly malfunction, however, resulting in a renewed threat to the safety of the aircraft.
It is not always apparent that a suppressor is malfunctioning, and it is not always a simple matter to check the operation of the suppressor because of its location. The suppressor is mounted to an engine, which in turn is typically mounted relatively high on a pylon of the helicopter. A means of checking the operation of the suppressor at ground level and from a remote location would be desirable.
It is known that an engine is a heat source and as such it emittes infrared radiation. A detection of the infrared radiation can therefore be employed as a measure of the heat intensity from the engine, and accordingly as a check on the operation of the engine suppressor. Infrared detectors are known. See, for example, U.S. Pat. Nos. 3,992,943; 4,081,678 and 4,121,459. What is needed is a detector which will detect the infrared radiation emitted by an engine while compensating for varying engine power. The detector should be portable as it will have to be used in hostile areas. It must be capable of quickly and accurately indicating the level of infrared radiation, and indicating whether or not the infrared radiation level is at a safe level for a given engine power setting.